With regard to a vehicle air conditioner unit disclosed in JP-A-10-35251, as shown in FIG. 6, an air conditioner unit case defines a heated air passage through which air heated by a heating device 110 flows and a cooled air passage through which air cooled by the cooling device 100 flows while bypassing the heating device 110. An air mix door 120 is provided upstream of the heating device 110 with respect to an air flow direction. The air mix door 120 adjusts a ratio of a volume of air to be heated by the heating device 110 to a volume of cooled air flowing in the cooled air passage, thereby controlling the temperature of air to be blown into a passenger compartment.
Further, to improve mixing of the cooled air and the heated air, a guide wall 130 is provided at a position downstream of the heating device 110. The guide wall 130 directs the flow of the heated air toward the cooled air passage so that the heated air merges with the cooled air of the cooled air passage at a substantially right angle.
However, the guide wall 130 is arranged to extend between the heated air passage and a foot opening 140. In a foot mode shown in FIG. 6, the heated air flows toward the cooled air passage along the guide wall 130 and then turns at the end of the guide wall 130 toward the foot opening 140 as denoted by an arrow A. As a result, resistance of the air flow is likely to be increased, and therefore the volume of air to be blown into the passenger compartment is reduced. Furthermore, this may result in an increase in noise.